Wing panels for commercial jet transport airplanes are typically built up from long aluminum "planks" connected together along longitudinal adjacent edges with splice stringers and stiffened with parallel stringers extending longitudinally of the wing. Empannage horizontal stabilizer panels are also stiffened with stringers. The stringers are spaced approximately 6"-8" apart chord-wise over the entire surface of the wing panel and are fastener to the wing planks by rivets or other fasteners approximately every 1"-2" along the length of the stringers. A typical commercial jet transport of about 300 seat capacity will have about 300,000 rivets fastening the stringers and splice stringers to the wing planks to make up each of the upper and lower wing panels, so it is imperative for an efficient wing fabrication facility to high speed accurate equipment for drilling and fastener installation with a minimum of manually installed fasteners and rework.
In the classical wing panel fabrication process, the wing planks are fixtured in position and are temporarily fastened together with stringers and tack fasteners on an apparatus similar to that shown in U.S. Pat. No. 4,894,903 to Woods. Tack fasteners are placed about every 20" to hold the wing panel planks together securely enough to move them to a riveting machine where the tacked-together wing panel is laid on horizontal headers which support it at the desired compound curvature for drilling and rivet installation to permanently fasten the stringers to the wing planks. Afterward, the temporary tack fasteners are removed and replaced with permanent fasteners.
This classical process is very wasteful of factory floor space since the wing panel is supported in a stationary horizontal position during riveting. It also requires large and expensive equipment to perform the riveting, since the drilling and riveting machine must be capable of precise movements in five axes over the entire length and width of the wing. The panel fixturing and temporary fastening are typically performed on a panel jig having hard tooling to locate the stringers and planks. Panel jigs are expensive tools and are each dedicated to only a single airplane model. The operations on the panel jig are performed in the vertical orientation, but the assembled wing panel must then be "flown" to the wing riveting machine and accurately indexed thereon, which requires large and expensive crane equipment and takes an entire shift to accomplish the transfer, during which both the fixturing jig and the wing riveter are out of production. During indexing of the assembled wing panel on the headers of the wing riveter, the expensive wing riveter is sitting idle. Thus, the existing is labor intensive, slow, and requires an inefficient use of expensive factory floor space and equipment.
Several attempts have been made in the past to provide apparatus that is capable of riveting stringers to wing panels in a vertical orientation. U.S. Pat. No. 4,864,702 to Speller, Sr. et al. and U.S. Pat. No. 5,033,174 to Zieve disclose apparatus for holding the wing panel in a stationary vertical position while a gantry or yoke moves along the wing and moves tools vertically or chord-wise to perform operations on the wing panel. These devices accomplish the desirable saving of factory floor space but require a complicated and expensive mechanism for vertically moving the tooling to position it at the desired rivet installation height chord-wise of the wing panel. The modern requirements for extreme positioning precision of the stringers and ability to record statistical data regarding hole parameters increases the cost involved in adding the vertical movement capability into the moving gantry or yoke.